Every dental unit is equipped with small-bore plastic tubing to bring water to the air/water syringe, the ultrasonic scaler, and the high-speed hand piece. Because of the formation and subsequent sloughing off of microbial biofilms from the inner surfaces of the plastic tubing, dental water is heavily contaminated with microorganisms and endotoxin. During dental procedures, the contaminated water will be aerosolized by dental equipment to spread the microbes and endotoxin into air. Dental health care personnel (DHCP) are exposed to these occupational biohazards repeatedly on a daily and long-term basis, which could cause respiratory infection, occupational asthma, and even fatality in DHCP. The long-range goal of this project is to use N-halamine-based rechargeable antibiofilm tubing to control the formation of dental unit waterline biofilms so as to reduce occupational exposure of DHCP to the biohazards. N-halamines have antimicrobial efficacy similar to that of hypochlorite bleach, one of the most widely used disinfectants in dental and hospital settings, but N-halamines are more stable, less corrosive, and have much less tendency to generate halogenated hydrocarbons. It is anticipated that after covalently binding N-halamines onto plastic tubes, the new tubes will be able to inactivate any approaching planktonic cells to prevent microbial adhesion/colonization, the first step in the formation of biofilms. Thus, the tubes'inner surfaces will be free of biohazards during dental operations, improving the microbial quality of dental unit water and aerosols. The antibiofilm activity is anticipated to be stable for a reasonably long period of time (e.g., more than a month), and if it is lost due to extensive use, the tubing can be easily recharged by a hypochlorite bleach treatment when the dental units are not in use to regenerate the antibiofilm function. The specific aims of the proposed R03 study are to: (1) develop N-halamine-based antibiofilm dental unit waterline tubing;and (2) evaluate the efficacy and safety of the new tubes in model dental water delivery systems. To achieve these goals, the first part of the proposed research will covalently bind N-halamine precursors into plastic tubing currently used in dental clinic waterlines, so as to introduce antimicrobial effects into the tubing to achieve long biofilm-controlling durations. This will be followed by a series of studies to provide detailed information on the mechanical properties, antimicrobial activity, rechargeability, and effects of recharging on the mechanical properties of the new tubes. Then the new tubes will be evaluated with mixed species of water bacteria in model dental water delivery systems to determine the efficacy and safety of the new approach in reducing occupational exposure of DHCP to waterborne and airborne microorganisms and endotoxin. The antibiofilm tubing approach is an attractive advance in controlling dental unit waterline biofilms to improve the occupational safety and health of dental health care personnel. In addition, the antibiofilm plastic tube materials to be developed in this study may find applications in other clinically important surfaces, which will make significant contributions to a better and safer healthcare environment.